Longitudinal study of behaviour disorders in low birthweight infants

Aim-To compare the prevalence of childhood and adolescent behavioural problems in low birthweight infants with matched controls. Methods-A cohort study of a geographically defined population of survivors of less than or equal to 1500 g birthweight born in 1980 and 1981 and age, sex, and school matched controls was undertaken. Children with a clinical disability were excluded. Data from Rutter questionnaires, completed by parents and teachers when the children were aged 8 and again at age 14 years, were assessed. Results-From an initial 40 321 births in 1980-81 there were 399 of birthweight less than or equal to 1500 g, of whom 219 survived to age 8. After exclusion of the 42 children with clinical disability, 177 cases comprised the sample. Of these, 10 (6%) refused or could not be contacted, leaving 167 cases for each of whom a matched control was obtained. At age 11 years, both parent and teacher questionnaires showed an increased prevalence of behavioural problems in cases compared with controls. The presence of a pervasive behavioural problem, when the responses of parents and teachers were concordant, was present in 9% of cases and 3% of controls. There were 132 pairs where the cases and controls were the same at ages 8 and 14 years and provided longitudinal data. The parental questionnaire showed there was a significant decrease in the prevalence of behavioural problems for cases and controls between the ages of 8 and 14 years. There was almost no longitudinal change in the prevalence of behavioural problems as shown by the teacher questionnaires. Conclusion-Although low birthweight infants are at increased risk of behavioural problems, because they comprise only a small proportion of all births, their population attributable risk for behavioural disorder is around 2-3%.